1. Technical Field
The present invention relates generally to pet toilet units, and more specifically to a completely disposable toilet unit, one aspect of which is that upon becoming sufficiently soiled by liquid and solid waste, the toilet unit can be easily discarded.
2. Description of the Background Art
Many people, especially those in urban environments, must leave their pets indoors for periods of time and the animals are required to eliminate their waste within the enclosed, interior environment. Often this period of time lasts for many days, but most often the time is 10 to 12 hours each day which reflects the period required for full time employment and travel to and from the workplace. Therefore, the need for a better short term and convenient accommodation of animal waste products and their disposal for confined and unattended pets is required.
The well known solution to this problem has been the animal litter box. The basic device is a shallow open container most commonly containing an absorbent granular or pelletized material ("litter"), which material is disposed of periodically as it becomes soiled. Common litter materials include clay, diatomaceous earth, and alfalfa; less common materials include peat, fly ash, cedar chips, and various pelletized materials such as paper, sawdust, and polyethylene foam. There are a number of problems associated with the basic device and its component parts, some of which have been addressed with limited success by various prior refinements.
The utilization of absorbent clay, by far the most commonly used litter material, has a number of problems. It is heavy and inconvenient to use and, in addition to frequent spills, dust is discharged into the air when it is poured into and out of the litterbox. When the box is used, the animal's natural instinct to bury the fecal matter and urine causes it to kick the litter out of the box, raise more airborne dust, and make a mess. Other less popular materials used for litter such as diatomaceous earth and fly ash have the same characteristics. In addition, all of these granular mineral products are unsanitary and are not recommended for use by veterinarians after animal surgery (especially the common claw removal for cats) as they are likely to cause infection. When a permanent litter box with a disposable plastic sheet liner is used (by far the most common assembly for domestic cats), a sufficient depth of granular material must be utilized to protect the liner from tearing due to the digging/burying instinct. This amount of material, in turn, requires the plastic liner to be sturdy enough to lift the material out of the box, thereby making the liner more expensive.
Other pelletized or granular materials made of organically derived byproducts, including pelletized paper, alfalfa, peat, sawdust, et. al., have been suggested to overcome the weight and dust problems of the granular minerals, but the light weight of these products exacerbates the problem of litter scattering and liner tearing, and many of them do not create a desirable texture for the animal to walk upon or utilize as a toilet.
An additional problem with all pelletized litters is the lack of portability. With the increase in mobility of the population, pets are often moved or taken on vacation requiring a portable animal toilet. Having to carry a bag of litter, liner, and litter box and having to set up and dispose of the assembly at a motel is often an exercise in creative logistics and always a serious inconvenience. Mack, U.S. Pat. No. 4,800,077 Jan. 31, 1989, proposes an animal waste collection pad with a frangible capsule which when broken will attract dogs; because of its flat sheet configuration and lack of attractive texture it is not likely to be either noticed or utilized by cats or other animals.
Providing a cover over the litter box has been proposed to eliminate the scattering problem of pelletized litter materials and contain odors, but these boxes are bulky in size and require constant cleaning. Covered boxes do not work well because animals resist going into a small enclosed space for elimination, preferring as open an outdoor space as possible for two reasons: it is the instinctual opposite of denning which prefers a closed space and animals will not soil a den; and, if the container has been previously used, there are always lingering odors which are also a deterrent. In addition, as the waste ages in the confined space, the odor concentration can get intense, and the animal will be less likely to use the container.
Other prior litter box solutions propose various assemblies of parts including, Sweeney, U.S. Pat. No. 4,534,315 (1985) which discloses an assembly wherein nonabsorbent granules are layered over an absorbent layer, and Yahanton, U.S. Pat. No. 4,869,204 (1989) which discloses a three part assembly consisting of a screen to prevent tearing, an absorbent pad, and an impermeable plastic lining all of which is covered by a layer of granular litter. Brazzell, U.S. Pat. No. 3,752,121 is similar to Yahanton except that an impermeable artificial grass is used as a protective layer above the absorbent pad. Other related patents include U.S. Pat. No. 3,233,588 which utilizes a screen above the litter to collect feces and U.S. Pat. No. 3,809,013 which incorporates granular litter and a stack of liners. While many additional patents could be cited regarding other variations of assemblies, none of the known literature satisfactorily addresses the problems of either the portability or the scattering of pelletized litter and/or have not been commercially successful because they are too complex and costly, and require the maintenance and cleaning of the various component parts.
It is common knowledge and practice to use newspaper to house train dogs to eliminate in a chosen area and it is relatively well known that newspaper can be used in a litter box as a substitute for commercially available litter as an expediency. Indeed, the use of torn newspaper for litter is commonly recommended by veterinarians following surgery, so as to avoid the infections caused by granular mineral products entering the wounds. However, the use of newspaper for litter in sheet or torn form has some fundamental problems--In sheet form the litter is not appealing to animals (especially cats) because it surface texture is too smooth and it does not satisfy the digging/burying instinct. In addition, urine tends to stay on the surface as does fecal matter and both are likely to get tracked around the house. In addition, the waste products that are absorbed by the sheets stay wet and are not sufficiently aerated to dry out; the layers between the sheets become breeding grounds for odor causing bacteria and fungi. The sheets are not efficient absorbers of moisture because their exposed surface area is not great.
Tearing the newspaper into strips improves the performance of the newspaper as it increases the absorption area, creates pockets for aeration, and generates a more desirable texture for the animal. However, torn newspaper when laid in a litter box tends to get compressed, tangled, and matted together by the animal excrement. Walking upon it gradually makes it lay flat and it quickly loses most of its desirable characteristics. In addition, when shredded paper is used, it precludes the utilization of a waterproof liner as the digging/burying will cause tears due to the lack of protection which is provided by paper sheets, a sufficient depth of granular material, or (less commonly) protective screens or layers suggested by some of the more complex prior art assemblies cited above.
Torn or shredded paper, particularly absorbent paper such as newsprint has been successfully used as a substitute for straw or shavings for large ruminants such as cattle. It is more absorbent than straw or shavings which contain high percentages of non-absorbent cellulose fibers. However, its use for smaller animals has not been as effective, as the "bedding" when cut into long strips tends to become entangled and matted with excrement. Whitehead et al., U.S. Pat. No. 4,376,422 (1983), attempts to overcome this problem by cutting the paper into strips and varying the length of strips so that much of the material is in the form of diced paper 10 to 40 mm in width and up to 120 mm long. Although this invention claims to prevent tangling, it does not prevent the gradual compression and flattening of the material. Reducing the paper further to a particulate form creates particles which decompose on contact with urine into a pulp or mush which quickly loses its effectiveness. U.S. Pat. No. 5,001,600 attempts to obviate this problem by creating "tubular interlaced pellets" that have integral voids. Both the diced and pelletized paper would, of course, have the same scattering and textural problems mentioned previously if used in a typical open litter box.
It should be noted that the term "bedding" or "animal bedding" is similar in many respects to the term "litter" as they are both materials used to absorb animal waste. In common usage "bedding" is a material used in an animal confinement for both sleeping and absorbing waste products, "litter" is a single use material for waste only and the animal may be confined or not but does not sleep or live on it. For the purposes of the present invention, the words are considered interchangeable.
It is not new to take strips of material and attach them or weave them together to create a textured surface. Indeed, this is the configuration of cut pile carpet and fur-like fabrics. Additional, and perhaps more related applications, can be found including Elder, U.S. Pat. No. 2,505,176 (1950) where an artificial grass mat as a grave decoration is proposed.
The creation of loosely woven absorbent material is described in Charbonneau, French Patent No. 2 248 785 (1975) in which a loose mat of straw is woven with cellulose string to form a litter for ruminants and horses. This prior art, although tangentially applicable to the present invention, has only marginal utility as a pet toilet application. The problem with straw is that it is too messy a material to be utilized in a pet toilet and because of its high cellulose fiber content it is not sufficiently absorbent. If the methodology of construction were replicated utilizing a more suitable material such as shredded newspaper, there would be little improvement over the basic material as it would tend to lay flat and be subject to the matting and caking mentioned previously. Indeed, the only advantage of this material would be the elimination of loose fibers and the ability to gather and fabricate the strip material as a single and portable assembly.
It is common knowledge that a disposable liquid impermeable membrane or liner can be utilized to obviate the cleaning of the rigid permanent litter box container. When granular litter is employed, this plastic liner often doubles as a bag for disposal of the material. This liner can take the form of a simple sheet of plastic (the most common commercially available product) or in a variety of forms including U.S. Pat. No. 5,007,375 (1991), wherein the liner is in the form of a plastic bag which slips over the entire box; Sweeny, U.S. Pat. No. 3,227,137 (1966), wherein the liner is elaborately folded, slips over the box edge and after use becomes a disposal bag; and U.S. Pat. No. 4,779,566 (1988) which is similar to Sweeny, but incorporates a retainer below the lip of the permanent box. There are many other variations, including: Goldman et al., U.S. Pat. No. 3,227,137; Smith, U.S. Pat. No. 3,684,155; and Behringer, U.S. Pat. No. 4,279,217. All of these prior solutions provide an easy disposal method, but all are related to the containment of pelletized or granular litter and require a sturdy plastic to support the weight when the material is disposed of.